Characteristics of vegetation change and its relationship with climate in the Qilian Mountains over the past 40 years

doi:10.11755/j.issn.1006-7639(2024)-03-0385

Abstract

Abstract:

Under the condition of global warming, the vegetation growth state in the Qilian Mountains has significantly changed. Studying the relationship between vegetation and climate in the Qilian Mountains is crucial for ecological construction in northwest China. Based on GIMMS NDVI data and ERA5 temperature and precipitation data from 1982 to 2022, this paper analyzes the variation trend of NDVI in the Qilian Mountains and its correlation with climate factors. The results show that high NDVI values are mainly concentrated in the eastern section (0.6-0.8), and NDVI values gradually decreased from east to west. Over the past 40 years, NDVI in the Qilian Mountains has showed an overall increasing trend, primarily due to its significant increases during the growing season. However, NDVI decreased during the non-growing season in some parts of the middle and eastern Qilian Mountains. NDVI changes in the Qilian Mountains were generally and positively correlated with temperature and precipitation. However, during the growing season, NDVI and precipitation were negatively correlated in the eastern part of the Qilian Mountains, while NDVI and temperature were negatively correlated in the western part during the non-growing season. There is a significant coupling mode between NDVI in summer and temperature, precipitation during the corresponding period in the Qilian Mountains. Overall, the increase in temperature and precipitation has been beneficial to the rise in NDVI. However, the increase in NDVI during the growing season in the eastern Qilian Mountains is primarily attributed to the rise in temperature.

Key words: vegetation, NDVI, climate change, coupled mode, the Qilian Mountains

摘要：

在全球变暖背景下，祁连山植被生长状态发生了明显变化，研究祁连山植被与气候的关系对西北地区生态建设具有重要意义。基于1982—2022年GIMMS NDVI数据及ERA5气温和降水数据，分析祁连山地区NDVI的变化趋势及其与气候因子的相关性。结果表明，祁连山地区NDVI高值区主要集中在东段（0.6~0.8），并自东向西逐渐减小。过去40 a，祁连山地区NDVI整体呈增加趋势，主要由于生长季NDVI的显著增加，而在非生长季，祁连山中、东部部分地区NDVI呈减小趋势。祁连山地区NDVI的变化与气温、降水整体呈正相关关系，但生长季NDVI与降水在祁连山东部部分地区呈负相关，非生长季NDVI与气温在祁连山西部部分地区呈负相关。祁连山夏季NDVI与对应时段气温和降水之间存在显著耦合模态，气温和降水的增加整体上对NDVI增加有益，但祁连山东部地区生长季NDVI增加主要由气温升高所致。

关键词: 植被, NDVI, 气候变化, 耦合模态, 祁连山

CLC Number:

P463.22

YANG Fei, FENG Xiang, ZHANG Feimin, WANG Chenghai. Characteristics of vegetation change and its relationship with climate in the Qilian Mountains over the past 40 years[J]. Journal of Arid Meteorology, 2024, 42(3): 385-394.

杨斐, 冯祥, 张飞民, 王澄海. 过去40 a来祁连山地区植被变化特征及其与气候的关系[J]. 干旱气象, 2024, 42(3): 385-394.

Figures/Tables 12

Fig.1 The Qilian Mountains location map

Fig.2 The multi-year average of land use (a) and NDVI (b) during the growing season in the Qilian Mountains from 2000 to 2022

Fig. 3 Time series of annual average NDVI in the Qilian Mountains from 1982 to 2022 （The solid red line represents the 9-year moving average）

Fig.4 The spatial distribution of NDVI trends in annual (a), spring (b), summer (c), autumn (d) and growing season (e) in the Qilian Mountains from 1982 to 2022 (Unit: ×10-3 a-1) (the black slash areas passing the significance test at α=0.05)

Tab.1

NDVI变化量	年	春季	夏季	秋季	生长季
-0.004~0	10.19	39.30	7.90	15.37	7.69
>0~0.001	62.75	53.97	36.97	39.73	41.70
>0.001~0.002	23.67	5.28	32.89	27.18	34.19
>0.002~0.003	3.11	1.08	15.52	12.27	12.66
>0.003~0.004	0.25	0.29	5.54	4.24	3.25

Fig.5 The spatial distribution of the correlation coefficient r between NDVI and air temperature in annual (a), spring (b), summer (c), autumn (d) and growing season (e) in the Qilian Mountains from 1982 to 2022 (the black slash areas passing the significance test at α=0.05)

Tab.2

相关性	年	春季	夏季	秋季	生长季
显著负相关	0.32	4.36	1.61	0.14	2.29
不显著负相关	7.94	19.24	8.33	28.47	9.66
负相关	8.26	23.60	9.94	28.61	11.95
正相关	90.09	76.39	90.06	69.27	88.05
不显著正相关	33.12	39.34	28.47	59.76	30.47
显著正相关	56.97	37.05	61.59	9.51	57.58

Fig.6 The spatial distribution of the correlation coefficient between NDVI and precipitation in annual (a), spring (b), summer (c), autumn (d) and growing season (e) in the Qilian Mountains from 1982 to 2022 (the black slash areas passing the significance test at α=0.05)

Tab.3

相关性	年	春季	夏季	秋季	生长季
显著负相关	0.72	11.01	0.93	1.39	1.61
不显著负相关	13.80	51.14	18.06	43.88	14.99
负相关	14.52	62.15	18.99	45.27	16.60
正相关	85.48	37.84	81.01	54.72	83.40
不显著正相关	41.06	34.59	43.81	53.61	35.30
显著正相关	44.42	3.25	37.20	1.11	48.10

Fig.7 The spatial distribution of the correlation coefficient between NDVI and temperature (a, b, c) as well as precipitation (d, e, f) in the previous season in spring (a, d), summer (b, e) and autumn (c, f) in the Qilian Mountains from 1982 to 2022 (the black slash areas passing the significance test at α=0.05)

Tab. 4

相关性	气温			降水
相关性	春季	夏季	秋季	春季	夏季	秋季
显著负相关	1.18	4.36	6.68	1.57	0.58	1.51
不显著负相关	40.34	19.24	24.96	47.07	15.34	13.05
负相关	41.52	23.60	31.64	48.64	15.92	14.56
正相关	58.51	76.40	68.35	51.36	84.09	85.44
不显著正相关	52.83	39.34	42.74	48.39	64.81	38.20
显著正相关	5.68	37.06	25.61	2.97	19.28	47.24

Fig.8 The spatial distribution of the time coefficients (a, d) corresponding to the first mode of the SVD of NDVI and simultaneous air temperature (a, b, c) and precipitation (d, e, f) in the Qilian Mountains from 1982 to 2022, as well as the anisotropic correlation coefficients of NDVI (b, e) and simultaneous air temperature (c) and precipitation (f)

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